Sports Direct, the clothing retailer led by Newcastle United's owner, Mike Ashley, is making its biggest foray abroad to date with the acquisition of controlling stakes in Austrian and Baltic sports chains.

The company has agreed to buy a 51% share in Austria's Sports Eybl & Sports Experts, known as EAG, for €10.5m (£8.9m) as well as take on €30m of its debts.

The group has 58 stores with a turnover of €323.8m, and is the largest overseas chain in Sports Direct's portfolio.

Sports Direct has also acquired a 60% stake in Sportland International Group, the largest sporting goods retailer in the Baltic states with a turnover of €61.6m and 80 stores.

Sports Direct did not disclose how much it paid for the company, which operates the Sportland, Sportland Outlet, Timberland, O'Neill, Nike and Nike Outlet retail chains in Estonia, Latvia and Lithuania, as well as being a distributor for Nike.

Dave Forsey, Sports Direct's chief executive, said: "Expected benefits from these investments include increased scale for our international business, growing international awareness of our group brands and additional expertise in specialist product categories such as winter sports."

Until now Sports Direct's biggest overseas market has been Belgium, where it owns 46 stores. The company will now operate in 16 countries, including Portugal, France and Slovenia.

Analysts said the acquisitions were relatively small in the context of Sports Direct, but showed the extent of Ashley's ambitions outside the UK.

Those ambitions are clear in Sports Direct's five-year option to acquire the rest of EAG for €15.5m from its new partners, the Eybl group.

The City broadly welcomed the deal, although the shares dipped 1.74% to 509p on Wednesday.

Kate Calvert, a retail analyst at Cantor Research, said: "We have become concerned of late that the recent spate of acquisitions may take management focus away from developing a dominant online business."

Sports Direct has thrived in the UK by offering low prices and leveraging sports brands it has bought out, including Dunlop, Slazenger and Karrimor. Sales have also been boosted by a generous share bonus scheme which is due to pay out this summer.